The Cardiovascular Health Study is a population-based, longitudinal study of risk factors for the development and progression of coronary heart disease and stroke in adults over the age of 65 years. Both risk factors established in middle-aged population and suspected risk factors are examined and include hypercholesterolemia, hypertension, glucose intolerance and diabetes, and cigarette smoking. Since atherosclerosis is prevalent in the elderly, the study focuses on factors thought to induce clinically overt disease. It does so in two ways: (1) It assesses the prediction of clinical disease from non-invasive measure of preclinical disease, such as carotid atherosclerosis, left ventricular impairment, and arrhythmias of episodes of myocardial ischemia. (2) Since cardiovascular events may occur in elderly people as a result of health or life circumstances which may have changed in the months preceding the event, the study contacts participants at frequent intervals to evaluate their status with respect to concurrent disease, social support networks, stressful life situations, diet, physical activity, and other risk factors. The study has three secondary objectives pertaining to the elderly populations: (1) to evaluate the factors associated with preclinical cardiovascular disease such as carotid atherosclerosis, left ventricular impairment and episodes of arrhythmia or myocardial ischemia; (2) to evaluate predictors of disability, institutionalization and mortality in participants who have coronary heart disease or stroke; and (3) to measure the utilization and impact of medical care services for coronary heart disease and stroke. Currently, risk associations are identified with clinical disease by the accumulation of events. Risk estimates are compared in subgroups of participants, such as women versus men, African-American versus Caucasian, those older versus younger than 75 years, or those with versus without prevalent clinical or subclinical disease. Risk estimates are compared in subtypes of disease, such as fatal versus non-fatal myocardial infarction, symptomatic versus silent myocardial ischemia, or fatal versus non-fatal stroke. Estimates are compared of longer-term (5-10 year) versus short-term (1-3 year) CVD risk. The study is also; determining whether presence or progression of subclinical disease (abnormalities detected non-invasively without signs or symptoms) are better predictors of clinical disease than traditional risk factors; identifying determinants of change in subclinical disease; identifying characteristics of subgroups at low risk for developing CVD (in whom preventive measures may be unnecessary). The primary objective of the Central Blood Analysis Laboratory is to develop and implement procedures to measure these risk factors, and to monitor performance of a protocol for their measurement in the blood of subjects with the elderly study. The secondary objectives of the Central Blood Analysis Laboratory are to: (1) to develop a Manual of Operations for Field Center technical staff involved in sample acquisition and processing and to develop a Manual of Operations for the CBAL staff to perform the selected determinations, (2) to standardize and maintain quality control for methods to obtain, process, ship, store and measure concentrations of activities of blood components from multiple site, and (3) to provide advice to the Project Steering Committee and NHLBI regarding the most useful selection of laboratory test (4) to assist in data analysis and preparation of study reports.